In conducting a heat resistance test of an IC component, called a burn-in test, it is conventional to place the IC component in a socket which, in turn, is connected to a circuit substrate and then to place the substrate into a heating device so that the temperature of the IC component can be raised to a selected level to conduct the test to thereby determine whether the IC component meets required specifications.
Typical prior art sockets used for this purpose comprise a base member formed of electrically insulative material in which an electrical contact element is mounted for each lead of the IC component to be tested. The contact elements are arranged in a selected pattern relative to an IC component mounting seat provided in the base and have movable contact portions adapted to move into and out of electrical engagement with respective leads of the IC component. Typically, a cover member is movably mounted on the base and is provided with structure which allows the contact elements to move away from the IC component mounting seat when the cover member is in an open position to allow placement of an IC component in and removal of the component from the socket. When the cover member is moved to a closed position the contact elements are caused to move into electrical engagement with the respective leads of the IC component.
One type of prior art socket comprises a cover member which is vertically movable in which the IC component is inserted or removed from the socket by pushing the cover member toward the base with the cover member camming an extension of each spring type contact element so that the contact making portion of each respective contact element is pivoted or swung away from the IC component's leads. When the cover member is allowed to return to a position away from the base under the influence of spring members, the contact making portion of the contact elements are allowed to move into engagement with the respective leads of an IC component received in the socket. This type of socket generally has certain limitations including an undesirable increase of inductance in the circuit and concomitant interference with adjacent contacts due to the particular complex configuration of the contact elements required to achieve the pivotal motion. Further, the structure is best suited for use with IC components which have only a single row of leads on any given side of the IC component.
Another type of prior art socket comprises a cover member which is pivotably mounted to the base with the cover held in a closed position by means of a latch. Leads of an IC component placed on the seat of the base are engaged by respective contact elements cammed by the cover as it is placed in the closed position. This type of socket, however, is not conducive to automation due to the rotational movement of the cover.
A particularly advantageous socket is shown in coassigned U.S. Pat. No. 5,470,247 in which a cover member is mounted for vertical motion on a base with latch members interconnected between the cover member and the base. The latch members are movable toward and away from movable spring contact elements mounted in the base in dependence upon the position of the cover member. The leads of an IC component are placed on top of respective movable spring contact elements when the cover member is in a pushed down position with the latch members pivoted away from the IC component seat. When the cover member is allowed to move vertically away from the base under the influence of spring members, the latch members are pivoted into engagement with the upper surface of the lead members of the IC component moving the lead members along with the movable spring contact elements downwardly a selected distance against the bias of the movable spring contact elements to provide a selected contact force.
As IC components become ever more dense, the number of electrical input and output connections required for the components increase. In order to accommodate significantly increased numbers of such electrical connections certain IC components are provided with a dense array of contact points disposed on the bottom surface of the components in place of conventional leads extending outwardly from sides of the components.